The smolt stage — when juvenile Atlantic salmon transition from freshwater to seawater — is a physiologically vulnerable period with significant welfare implications, as the stresses of smoltification are compounded by handling, transport, and transfer operations.
Smoltification represents a welfare-critical transition in farmed salmon production. Fish that are not physiologically ready for seawater transfer suffer acute osmoregulatory stress; fish that are ready but subjected to excessive handling or poor water quality during transfer experience compounded stress responses. The narrow timing window for optimal transfer, combined with the scale of operations at large salmon farms, creates pressure to prioritise operational efficiency over welfare. Farms that invest in real-time smolt readiness monitoring, minimise handling events around transfer, and provide optimal water quality during the transition period achieve both better welfare outcomes and better survival rates. These goals are aligned, not competing.